Fuel Issues....

Hey... I have a M923A1 that won't start.... It hadn't been ran in quite awhile, and the last time I drove it, it was sluggish and slow throttle response until it got warmed up. I'm guessing the fuel was getting bad.. (after thought now)

- I've replaced the main fuel filter
- Drained the tank and put in clean diesel - No Start
- Replaced the PT filter screen - No Start
- Disconnected the fuel lines from the PT, and hooked up a transfer pump into a clean 5 gal jerry can of diesel, turned on pump to apply pressure to the inlet of the PT - No Start
- Cracked open the Fuel T-Line going to the front and back of the motor... fuel sprays out
- Cracked open the Fuel line fitting at the front of the motor... fuel sprays out

What is the next step??? I'm guessing the next step is to remove the injectors? I'm definitely NOT a diesel mechanic, and have never cracked open one of these motors. I know the injectors are inside.. and have a timing, pushrods, adjustments, etc....

Is there any field trick to test, or clean the injectors without removing them?? Maybe crank straight Sea foam in it while trying to start it??

HELP?!?!?!

What was the issue last time ? you never updated your thread.
M923A1 Fuel problem... Won't start!

Have you tried to turn in the bypass knob on the electric fuel shut-off ?

You need to check how much fuel pressure is coming out of the injection pump? Simply saying fuel spray isn't definitive. Remove the shut off valve and use a 1/8th pipe fitting.

porkysplace said:

What was the issue last time ? you never updated your thread.
M923A1 Fuel problem... Won't start!

Have you tried to turn in the bypass knob on the electric fuel shut-off ?

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Yep, Tried that awhile ago. No change after screwing in the electric shutoff valve bypass screw... still no start.

simp5782 said:

You need to check how much fuel pressure is coming out of the injection pump? Simply saying fuel spray isn't definitive. Remove the shut off valve and use a 1/8th pipe fitting.

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How much fuel pressure / Flow rate should it have? I would think if it's getting fuel to the injectors, it should at least stumble start, try to start, something. When I crank it, it turns over quick, but not even attempting to start. Quick shot of either and it starts right up and dies immediately. So I know it's not a piston/compression issue. Not fuel in the oil... No oil/fuel in the water.... It just seems the injectors are not flowing. But I have zero experience or clue on pulling the injectors or reinstalling them.

Jayco36REQS said:

How much fuel pressure / Flow rate should it have? I would think if it's getting fuel to the injectors, it should at least stumble start, try to start, something. When I crank it, it turns over quick, but not even attempting to start. Quick shot of either and it starts right up and dies immediately. So I know it's not a piston/compression issue. Not fuel in the oil... No oil/fuel in the water.... It just seems the injectors are not flowing. But I have zero experience or clue on pulling the injectors or reinstalling them.

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Depends on what the rail pressure for the pump is.. anywhere from 140 to 180psi

^^ That is incorrect. A PT system has no pressure at idle, only a spike on acceleration. There will only be flow, measurable with a flow meter in lbs per hour. Rail pressure only happens when loaded.
No cracking lines needed, it is self priming.
PT screen filter is only there IF a pump failure happens, the debris does not get into the injectors. IF that fliter is plugged, it is from crappy old fuel, we're talkin YEARS old, or a failure in the pump.
Check voltage at the FSOV.
Make sure the emergency shut off is not off.
You say fuel sprayed from lines on the front and rear of the engine WITH a transfer pump hooked up, bypassing the pump? Just an FYI, upper is return, lower is supply from the pump.
Did you screw the bypass IN on the pump and try it?
Did you run a line from a bucket TO the pump and see if it fires?

WillWagner said:

Check voltage at the FSOV.
Make sure the emergency shut off is not off.
You say fuel sprayed from lines on the front and rear of the engine WITH a transfer pump hooked up, bypassing the pump? Just an FYI, upper is return, lower is supply from the pump.
Did you screw the bypass IN on the pump and try it?
Did you run a line from a bucket TO the pump and see if it fires?

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- Yes, as I stated above, the fuel transfer pump is in a Jerry can of new clean diesel, and connected into the PT pump inlet (Yes, the lower line that normally comes from the trucks filter)
- I never said I was bypassing the PT pump? That would be a crazy and defeat the purpose of troubleshooting. lol
- I used my transfer pump just to eliminate any concern of air leak or lack of inlet fuel flow. The transfer pump is low pressure, but flows at 10-gal a min.

- Yes, I've checked the emergency shut-off valve. I've never touched it. But double checked the lever and valve anyway.
- When I have someone cranking the engine, I cracked open the T-valve above the FSOV (that sends fuel to the front and back of the motor), and I get pressured fuel spray.
- Just for grins, I screwed in the FSOV, and tried the same above with no change in fuel spray, and still no start.

- What is the fuel flow rate of the PT while cranking? The only test I haven't done is disconnect the PT fuel outlet, and run a line into an empty bucket and see how much fuel flows per minute while cranking... But I don't know what it should be flowing at that point? My truck is a Red River rebuild with only 15k miles on it since rebuild. So I'm doubting the PT pump is bad... but who knows.

Unless there is something else I'm missing.... It is looking to possibly be an injector issue... or possibly a clogged injector screen? But removing and reinstalling injectors on this motor is WAY above my diesel skill set!! lol Anyone local willing to get this truck running, I'd be happy to pay for your time!! Or, if anyone local knows a diesel shop that makes house calls, I'd appreciate any leads. I can imagine the cost of a tow to a shop would be crazy high!!

I just want to get this truck back on the road!! Thanks!!

Your post seemed as though you bypassed the pump, no biggie. The only way to measure the cranking flow is on a pump stand. A trick to try and force feed rail pressure is to pinch/plug off the return line going back to the tank, do this as close to the engine as possible. It should make some measurable pressure then. Install a pressure gauge on the unused port of the fsov, a 200 lb one should do. If you get pressure and no smoke/start, most likely an injector issue. The filter screens on the injectors are for the same reason as the one in the pump, but, if the fuel was a mess and was sludge or algae filled, it could/can plug like all the filters on the engine. Injectors don't normally just fail to deliver fuel, something is wrong, it is a mechanical system. Has someone been inside the overhead

Have you found what happen to your truck cause I’m having the same issue

Farmerman28 said:

Have you found what happen to your truck cause I’m having the same issue

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I'm hoping to get the injectors out this Friday, clean the screens, inspect them, and see how it goes. If they look grunged up past the screens, I will likely take them over to a local injector shop to have them professionally serviced and flow tested.

Stay tuned!

btw... Thanks to several Steel Soldiers guys for giving good advice, and for the help!!

I ended up buying new Cummins injectors... Found a good deal and got all 6 for less than $400 all new sealed in original Cummins packaging. Great deal comsidering most places wanted over $400 EACH for true Cummins injectors!! sheesh

Jayco36REQS said:

I ended up buying new Cummins injectors... Found a good deal and got all 6 for less than $400 all new sealed in original Cummins packaging. Great deal comsidering most places wanted over $400 EACH for true Cummins injectors!! sheesh

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Do you have top stops or non top stop injectors?